Azoic dyeing of leather



trite AZOIC DYEING OF LEATHER No Drawing. Application October 31, 1955 Serial No. 544,079

8 Claims. (Cl. 8-13) This invention relates to a method for dyeing leather and more particularly to a methodfor dyeing leather with azoic dyestuffs.

It has long been the desire in the trade to be able to dye leather in such a manner that the color is fast to washing, crocking and light. The conventional acid, direct and basic colors frequently lack the necessary fastness properties and often tend to bleed considerably when treated in a soap liquor. Such bleeding is of course detrimental to the color properties of the dyestuff in addition to introducing problems in connection with staining of adjacent areas or garments. Attempts have been made to dye leather by the azoic method, as for example by application of a Naphthol AS type coupling component and coupling with a diazo component. However, due to the high alkalinity of the coupling component treating liquor, the coupling component exhausted poorly, the conditions for efiicient coupling with the diazo component were improper, and the shades obtained were dull, weak, and of poor wash-, crockand light-fastness. Moreover, the quality of the leather was adversely affected, desirable properties therein being destroyed. In my copending application Serial No. 544,078, also entitled Azoic Dyeing of Leather, filed on even date herewith, there is disclosed and claimed a process comprising, in an azoic dyeing method, the step of treating leather with an azoic coupling component devoid of solubilizing groups and containing optionally, at least one aromatically bound free amino group, from an aqueous solution having an initial pH of more than 7 and less than 11, and a final pH of no more than 7.

It is an object of this invention to provide an improved process for the azoic dyeing of leather. Another object of this invention is the provision of an improved process for the production of leather dyed with azoic colors having good wash-, crock-, dry-cleaningand/or light-fastness properties. Still another object of this invention is the provision of an improved process for the azoic dyeing of leather which will produce uniform, level shades and will not adversely affect desirable properties in the leather. Other objects and advantages will appear as the description proceeds.

The attainment of the above objects is made possible by my discovery that, subject to the limitations hereinafter described, even stronger, more uniform dyeings are obtained when the process to which the above-identified copending application is directed is carried out in the presence of a formaldehyde yielding substance and, if desired, also in the presence of a lower alkyl amine or alkylol amine. The instant invention accordingly comprises a process for the azoic dyeing of leather comprising treating leather in the presence of a formaldehyde yielding substance and, if desired, a lower non-aromatic amine, with an azoic coupling component, devoid of solubilizing groups and selected from the class consisting of pyrazolones and aromatic hydroxy compounds capable of coupling, from an aqueous solution having an initial pH of more than 7 and less than 11, preferably less than atent ice 9, and a final pH of no more than 7, for example from 3 to 7 and preferably about 5, and then causing said coupling component to react with a diazotized aromatic primary amine compound. In addition to the above advantages, it has also been found that leather dyed in accordance with the process of this invention possesses an unusual softness.

The surface imperfections in the leather, usually emphasized by prior art dyeing methods, is minimized Whereby an upgrading affect is attained. Where the azoic coupling component employed in the instant invention contains at least one aromatically bound free amino group, still further improved results are obtained with respect to uniformity and levelness of dyeings, and fastness to dry cleaning.

In carrying out the process, the leather is first wet out in the usual manner with Water which may desirably contain a wetting agent. If the leather is highly acid, the addition of some sodium bicarbonate or other alkaline material to the wetting-out liquor is desirable to aid in neutralizing the acidity and preventing it from unduly affecting the pH of the coupling component treating liquor. The aqueous solution containing the coupling component is prepared by dissolving the coupling component with sufficient alkali, such as sodium or potassium hy droxide, to form the alkali metal salt of the coupling component plus a small excess to prevent too early hydrolysis, but insufficient to raise the pH value of the solution over the above-mentioned maximum allowable values. During impregnation of the leather with this solution, the pH of the solution is controlled to drop to about 7 or less. In most cases this must be accomplished by addition of acid, such as acetic, hydrochloric or preferably formic acid, during and preferably towards the end of the impregnation treatment. In some cases, this addition of acid may be dispensed with where the leather is sufficiently acid, for example as a result of a previous tanning or other treatment. The temperature of treatment may vary from about room temperature to about F., with durations of about 15 minutes to 1 /2 hours. Optimum conditions are dependent in any particular instance upon the nature of the leather and the treating agents employed, being readily determinable by a worker skilled in the art. With some coupling components, addition of a small amount of a water-soluble organic solvent such as ethyl alcohol, isopropyl alcohol, ethylene glycol and its monoethyl ether, or the like may be desirable to facilitate solution thereof. The addition of a wetting agent to the solution, or other additives, may be desirable in some instances.

From the above, it will be understood that the instant process, instead of employing a highly alkaline coupling liquor, requires regulation of the initial pH thereof, by direct adjustment and/or by suitable treatment of the particular leather being dyed, in such manner that it has a value of more than 7 and less than 11, preferably less than 9, and that the drop in the pH during treatment is sufficient to bring it to about 3 to 7, preferably about 5.

In carrying out the process of the instant invention, the formaldehyde yielding substance may be added to the treating solution before, after or simultaneously with the coupling component, but before the pH of the solution has dropped to 7 or less. Best results are obtained by treating the leather first with the formaldehyde yielding substance and then with the coupling component. Op erative formaldehyde yielding substances include formaldehyde, paraforrnaldehyde, hexamethylenetetramine, formaldehyde bisulfite and the like. These substances are applied in an amount sufficient to yield from about 0.1 to 5 g. of formaldehyde per square foot (measuring only one side) of the leather.

The coupling components operative in the instant in- 3 vention are the usual ice color coupling components well known in the art and devoid of solubilizing groups such as carboxylic or sulfonic acid groups, but excluding acylacetic acid arylides which are not useful in this invention. In general, these coupling components fall within the class of pyrazolone compounds and aromatic hydroxy compounds capable of coupling. As pyrazolones, there may be mentioned 1-phenyl-3-methyl-5 pyrazolone, 1-p-tolyl-3-methyl-5-pyrazolone, 3-methyl-5-pyrazolone, S-pyrazolone, 1,3-dimethyl-S-pyrazolone, 1-(p-chlorophenyl)-3-methyl pyrazolone, l-(p-nitrophenyD- 3- methyl-S-pyrazolone, 1- (o-methoxyphenol) -3-methyl-S- pyrazolone, l-(m-aminophenyl)-3-methyl-5-pyrazolone, l-methyl-S-pyrazolone, l-phenyl-S-pyrazolone, l-phenyl-5-pyrazolone-3-carboxylic acid methyl ester, l-phenyl 5-pyrazolone-3-carboxylic acid ethyl ester, and other pyrazolones unsubstituted or substituted in the 1- and/or 3-positions by non-solubilizing radicals. The aromatic (carbocyclic or heterocyclic) hydroxy compounds useful as coupling components herein contain an aromatic hydroxy group inducing coupling, usually in orthoor paraposition, preferably the former, to said hydroxy group, and generally include phenols, resorcinols, 1- and 2- naphthols, benzonaphthols, hydroxybenzofluorenones, and the like, in addition to arylides of fi-hydroxy aromatic carboxylic acids. Many such coupling components operative herein are disclosed in Diserens, Chemical Technology of Dyeing and Printing, volume 1, pages 213 through 222 (Reinhold Publishing Corp., 1948); Lubs, Chemistry of Synthetic Dyes and Pigments, pages 182 through 192 (Reinhold Publishing Corp., 1955); and Adams, Journal of the Society of Dyers and Colorists, volume 67 (1951), beginning at page 223. Illustratively, examples of arylides of ,B-hydroxy aromatic carboxylic acids which may be employed in the process of the instant invention are 3-hydroxy-2-naphthoic acid arylides, 3-hydroxy-2-anthroic acid arylides, 3-hydroxy- Z-carbazole carboxylic acid arylides, 3-hydroxy-2-furane carboxylic acid arylides, Z-hydroxy-llH-benzoialcarbazole-3-carboxylic acid arylides, hydroxydibenzothiophene carboxylic acid arylides and the like.

As disclosed above and in said copending application, those azoic coupling components containing an aromatically bound free amino group enable the attainment of further improved results. Typical amino substituted couplers include aminonaphthols, such as l-amino-7- naphthol; aminophenols, such as m-diethylaminophenol,

aminoresorcinol, m-aminophenol; aminoazophenols and naphthols, such as 6-hydroxy-4(o-nitrophenylazo)-lnaphthylamine; aminophenylpyrazolones, such as methyl mand p-aminophenylpyrazolone; o-hydroxycarboxylic acid arylides having an amine substituent in the aryl radical, such as 3'-amino-3-hydroxy-2-naphthanilide. In general, the amount of coupling component employed depends upon the depth of shade desired, and usually falls within the range of about 0.001 to 2.5 g. per sq. ft. of leather.

To produce the azoic color on the leather, the coupling component must be reacted with a diazotized aromatic primary amine compound also devoid of solubilizing groups suchas carboxylic or sulfonic acid groups. As examples of such primary amine compounds useful in the instant invention, there may be mentioned aminoazotoluene, 4-chloro-2-nitroaniline, 5-chloro-o-toluidine, 4-nitro-o-toluidine, 2,5-dichloroaniline, 4-benzamido-2,5-- diethoxyaniline, 4-nitro-m-anisidine, 4-nitro-o-anisidine, 4-chloro-o-anisidine, 1 amino naphthalene, l-aminoam thraquinone, dianisidine, 5 chloro 4 nitro-o-anisidine, aminobenzophenones, aminosulfones such as aminobenzosulfones and aminodiphenylsulfones, aminodiphenyl ethers, aminocarbazoles, and other similar cyclic compounds containing at least one diazotizable primary amine group. These and other 'carbocyclic and heterocyclic azoic bases operative in the process of this invention are well known in the art.

As further distinguished from the process of the abovementioned copending application, and in view of the use of a formaldehyde yielding substance, where an in situ diazotiz'ation and coupling reaction is desired, the leather containing the coupling component, formaldehyde yield ing substance, and, optionally, the lower non-aromatic amine should be treated in a separate bath with the diazotizable aromatic primary amine compound followed by treatment with sodium nitrite and acid, preferably formic acid. I

Improved results may also be obtained by application to the leather containing the coupling component of the said aromatic amine in the form of its already diazotized compound, whereby a subsequent diazotization with sodium nitrite and acid is avoided. The diazo compound may be employed as a solution freshly prepared from a diazotizable aromatic amine or as a solution of one of its stabilized salts, e.g., as a hydrochloride or sulfate of one of the relatively stable diazos, as a double salt employing such salts as zinc chloride, Zinc sulfate, cadmium chloride, tin tetrachloride, fiuoroborates and the like, or as a salt with an organic sulfonic acid such as benzenedisulfonic acid, fl-naphthalenesulfonic acid and naphthalenetrisulfonic acid. In some instances wherein solubility may be insufficient a dispersing agent may be added to improve dispersion and penetration. Or the subsequent application of the said aromatic amine may be in the form of its nitroso compound or as the stabilized diazo amino compound, e.g. the Levamines. All of these forms of stabilized diazotized aromatic primary amino compounds or nitrosoamines are to be regarded as the equivalent of the freshly prepared diazotized aromatic primary amine compounds since they react as such with the coupling component.

Alternatively, said aromatic primary amine compound can be applied to the leather in its diazotized form simultaneously with the coupling component in known manner. Thus, the coupling component can be combined with a stabilized form of the diazotized aromatic primary amine compound, such stabilized compound being then activated by a drop in the pH to 7 or less whereby the coupling reaction takes place in situ on and/or in the leather. Examples of known types of combinations of coupling components and stabilized diazotized aromatic primary amine compounds are the Rapidazols (mixtures of couplers and diazosulfonates), the Rapid Fast colors (mixtures of couplers and antidiazotates), and preferably, the Rapidogens (mixtures of couplers and diazo amino compounds).

In carrying out the process of this invention, the initial pH of the solution containing the coupling component may be as high as 11 if the leather is highly acid. However, in most cases, wherein the leather has been washed free of salts or neutralized with an alkaline substance, the initial pH is usually in the alkaline range, and about 9. Where Rapidogens are used, the pH range should be between about 7.5 and 8 for optimum treatment since if the pH is lower the diazo tends to split and if higher, on subsequent addition of acid, acidification occurs unevenly which results in dull dyeings.

In general, the diazotized aromatic primary amine compound and the coupling component are employed in amounts sufficient to react in approximately equivalent proportions, although in some cases, it may be desirable to use an excess of one. In some instances, as when employing Levamines or Rapidogens, subsequent acidification of the treated leather to a pH of 3-4 is necessary to develop the color of the final dyestutf.

As a further feature of this invention, it has also been found that when a water soluble or readily waterdispersible lower non-aromatic amine is applied to the leather in the process of the instant invention prior to reaction of the coupling component with the diazotized aromatic primary amine compound, still stronger, more brilliant and more uniform dyeings are. obtained. The

non-aromatic amine may be added to the treating solution before, after or simultaneously with the formaldehyde yielding substance, but before the pH of the solution has dropped to 7 or less. Best results are obtained when said non-aromatic amine is added after the formaldehyde yielding substance and coupling component have been applied. As examples of such amines useful in the process of the instant invention, there may be mentioned mono-, diand triethanolamines, monoand di-methyland ethyl amines, diethylethanolamine, 2 methyl 2 aminopropanol, butylamine, pentylamine, cyclohexylamine, and the like. It will be seen that these amines are of a non-aromatic, aliphatic (including cycloaliphatic) character containing no more than about 6 carbon atoms. In general order of preference, monoethanolamine is first, with diethanolamine next. The amount of non-aromatic amine employed may vary from about 0.1 cc. to 2 /2 cc. per sq. ft. of leather. If the nonaromatic amine is gaseous, the equivalent amount is employed in the form of its salt, for example the hydrochloride, or in solution.

The following examples are illustrative of the instant invention and are not to be regarded as limitative. Proportions employed herein and in the appended claims are by Weight unless otherwise indicated.

Example 1 A 1 sq. ft. sample of chrome tanned syntan stained leather is treated for a few minutes in 1000 cc. water containing cc. 40% formaldehyde. To this bath is then added 1 g. 3-hydroxy-2-naphthoic acid o-anisididc dissolved with 2 cc. alcohol and /2 cc. caustic soda 24 B. for about 5-10 minutes at 120 F. To this bath is then added 2 /2 cc. monoethanolamine. The pH of the bath is about 11. The leather is worked in the bath for about -30 minutes at about 120 F., at which time the pH of the bath has ranged from about 10.5 to 9. cc. formic acid (10% solution) is then added and treatment continued for another minutes at 120 F., at which time the pH has dropped to about 6. The leather is removed and rinsed. The leather is then immersed in a bath containing 3 g. 4-nitro-o-toluidine diazonium fluoroborate in 1000 cc. water, for 60 minutes at room temperature, rinsed and finished as usual. The leather is dyed a brilliant, intense red with improved fastness properties on both the grain and the flesh.

Example 2 This example is the same as Example .1 except that 1 g. S-hydroxy-Z-naphthoic acid m-nitroanilide is used instead of the o-anisidide and 3 g. zinc chloride double salt of the diazo of 5-nitro-oanisidine is used instead of the said diazonium fiuoroborate. A bright deep red shade of improved fastness properties is obtained.

Example 3 This example is practically the same as Example 1, except that 1 g. of the compound of the formula:

Example 4 This. example is the same as Example 3, except that /2 .g. of a-naphthol is used as the coupler compound,

and 3 /2 g. azo-o-toluidine diazo as the sulfate is employed as diazo. A deep reddish brown coloration of improved fastness properties is obtained.

Example 5 This example is similar to Example 3, except that /2 g. resorcinol is used as coupler and 3 g. p-(p-methoxyanilino)-benzenediazonium chloride as the diazo. Instead of sodium acetate, 25 cc. sodium bicarbonate solution 10% is used. A deep brown coloration of improved fastness properties is obtained.

Example 6 This example is similar to Example 5, except that /2 g. 4- (o-nitrobenzeneazo -7-hydroxy-l-naphthylamine is used as the coupler compound and 4-benzamido-2,5-diethoxy benzenediazonium chloride zinc chloride double salt as diazo. A uniform black of improved fastness properties is obtained.

Example 7 A 1 sq. ft. sample of chrome tanned suede calf is treated in 1000 cc. water containing 5 cc. formaldehyde for 5 minutes at 130 F. To this bath is then added 1 g. 3-hydroxy2-naphthoic acid o-toluidide dissolved in 2 cc. alcohol and /2 cc. caustic soda 34 B. The bath has a pH of about 9. Treatment is continued for 30 minutes. To the bath is then added 25 cc. formic acid 10% solution and treatment continued for another 30 minutes, at which time the pH has dropped to about 5. The leather is rinsed and developed in a bath consisting of 3 g. o-chlorobenzenediazonium chloride zinc chloride double salt dissolved in 1000 cc. cold Water. After about 60 minutes, the leather is rinsed Well and finished as usual.

A bright orange dyeing is obtained of improved fastness properties and greater intensity and uniformity than is possible without the use of formaldehyde.

Example 8 This example is the same as Example 7, except that instead of using 5 cc. 40% formaldehyde solution, 2 /2 g. paraform is used. A similar uniform level dyeing results,

Example 9 A 1 sq. ft. sample of chrome tanned syntan stained sheep skin is treated in 1000 cc. water containing 5 cc. 40% formaldehyde solution for 10 minutes at F. To this is added 1 g. 3-hydroxy-2-naphthoic acid o-toluidide dissolved With 2 cc. alcohol and /2 cc. caustic soda 34 B. The bath is at a pH of about 11. After about 10 minutes 2 /2 cc. butylamine is added. The bath is then at a pH of about 10. After another 20 minutes, 25 cc. formic acid 10% solution is added. After about 30 minutes, the pH of the bath has dropped to about 6. The leather is rinsed and developed in a fresh bath consisting of 3 g. p-nitrobenzenediazonium p-chlorobenzenesul'fonate dissolved in 1000 cc. cold water. After about 30 minutes the leather is rinsed and finished as usual. A deep red shade of improved fastness properties is obtained.

When the butylamine of this example is substituted by other amines, e.g. monoethanolamine, diethanolamine, triethanolamine, diethylethanolamine, dimethylethanolamine, 2-methyl-Z-aminopropanol, dimethylamine, or cyclohexylamine, commensurate results are obtained. Monoethanolamine gives the best dyeing results.

Example 10 A 1 sq. ft. sample of chrome tanned glove leather is treated with 1000 cc. Water containing 5 cc. formaldehyde 40% solution at 120 F. for 10 minutes. To this bath is added 1 /2 g. of a Rapidogen mixture comprising 5- chloro-o-toluidine diazo stabilized with sarcosine, and 3- hydroxy-2-naphthoic acid o-toluidide dissolved in 3 cc. alcohol and A2 cc. caustic 34 B. After about 10 minutes 2 /2 cc. monoethanolamine is added. The bath is at a pH of about 8. Treatment is continued for 20 minutes and then 25 cc. formic acid 10% solution is added. This treatment is continued for about 30 minutes, at which time the pH has dropped to about 6-6.5. The leather is rinsed and finished as usual. A bright red, uniform dyeing of improved fastness properties is obtained.

Example 11 A 1 sq. ft. sample of chrome tanned glove leather is treated with 1000 cc. water containing cc. formaldehyde 40% solution at 120 F. for minutes. To this is added .75 g. 3-hydroxy-2-naphthoic acid o-toluidide dissolved with 2 cc. alcohol and /2 cc. caustic 34 B. After about 10 minutes 2 /2 cc. monoethanolamine is added and treatment continued for minutes, at which time the pH is about 9-10. Then cc. formic acid 10% solution is added and treatment continued for minutes, at which time the pH has dropped to about 5-6. The leather is rinsed and transferred to a fresh bath which consists of .8 g. 5-chloro-o-toluidine diazo stabilized with 4-sulfoanthranilic acid in 1000 cc. cold water. After about 30 minutes 5 cc. formic acid 10% solution is added. After another 30 minutes the leather is rinsed and finished as usual. A bright red, uniform dyeing of improved fastness properties is obtained. When the Levamine of this example is replaced by other Levamines, e.g. 5-ch1oro-oanisidine diazo stabilized with N-methyl-S-sulfoanthranilic acid, 4-benzamido-2,5-diethoxyaniline diazo stabilized with sarcosine, or 4-(o-tolylazo)-o-toluidine diazo stabilized with methyltaurine, commensurate results are obtained.

Example 12 A 1 sq. ft. sample of chrome tanned glove leather is treated with 1000 cc. water containing 5 cc. formaldehyde 40% solution at 120 F. for 10 minutes. To this bath is added .75 g. 3-hydroxy-2-naphthoic acid o-toluidide dissolved with 2 cc. alcohol and /2 cc. caustic 34 B. After 10 minutes 2 /2 cc. monoethanolamine is added. The bath is at a pH of about 9.5-10. After 20 minutes 25 cc. formic acid 20% solution is added. After 20 minutes, the pH has dropped to about 5.6. The leather is rinsed and dyed at room temperature in a bath consisting of 1 g. nitroso 2,5-dichloroaniline in 1000 cc. water at room temperature for 60 minutes. A bright orange shade of improved fastness properties is obtained. Similarly good dyeings result when other nitrosamines are used, e.g. nitroso 5-chloroanisidine and nitroso dianisidine.

Example 13 A 1 sq. ft. sample of chrome tanned suede sheep skin is treated with 5 cc. formaldehyde 40% solution in 1000 cc. water at 120 F. for 10 minutes. To this is added 1.5 g. of a composition comprising p-(p'-anisyl)-aminobenzencdiazoniurn arylsulfonate and 3-hydroxy-2-naphthoic acid anilide dissolved in 3 cc. alcohol and /2 cc. caustic 34 B. After 10 minutes 2 /2 cc. monoethanolamine is added. The bath is at a pH of about 8-8.5. After 20 minutes 25 cc. formic acid 10% solution is added. After further treatment for about 30 minutes, the pH has dropped to about 6-6.5, and a blue dyeing of improved fastness properties results. A similar dyeing in which the formaldehyde treatment is omitted, fails to develop color.

Example 14 3 dozen chrome tanned syntan stained goat skins, about 240 sq. ft. (21 lbs), are treated in sufficient water to float the skins containing 1200 cc. 40% formaldehyde solution at 120 F. for 15 minutes. 21 g. S-hydroXy-Z- naphthoic acid m-nitroanilide and 21 g. 3-hyclroxy-2- naphthoic acid o-phenetidide are dissolved with 150 cc. alcohol, 25 g. dry caustic and 300 cc. water and the resulting solution added to the treating bath. After 15 minutes, 300 cc. monoethanolamine is added. The pH of the bath is about 9. After 30 minutes, 150 cc. formic acid solution is added. After 30 minutes, the pH has dropped to about 6. The skins are removed and developed in a bath consisting of 150 g. diazotized S-nitroo-anisidine stabilized as the zinc chloride double salt in suflicient water in the cold. After 60 minutes the skins are rinsed and then after-treated at 120 C. for 15 minutes with soda and soap to remove undesirable decomposition products and loose color, and finally rinsed, acidified and finished as usual. A beautiful bright pink of improved fastness properties is obtained.

Example 15 1% dozen chrome tanned syntan stained goat skins are treated in sufiicient water to float the skins containing 600 cc. formaldehyde 40% solution at 120 F. for 10 minutes. To this is added a solution containing g. resorcinol and 60 g. 1-phenyl-3-methyl5-pyrazolone dissolved with 300 cc. alcohol and 42 g. caustic soda (dry) and 300 cc. water. The bath is at a pH of about 8.

After 30 minutes 150 cc. formic acid 85% solution is added. After 30 minutes, the pH has dropped to about 5. The skins are rinsed and developed in a cold bath consisting of sufficient water in which is dissolved 1350 g. 4-(o-tolylazo)-o-toluenediazonium sulfate for 60 minutes. The skins are rinsed, after-treated with soap and soda, rinsed, acidified and finished as usual. A deep rich coppery rust of improved fastness properties is obtained.

Example 16 A 1 sq. ft. sample of chrome tanned syntan stained sheepskin was Wet back. In the dyebath which contained sufiicient water to float the skin was added 5 cc. formaldehyde (40% by volume). After 10 minutes at F. there was added 1.5 g. 3-hydroxy-2-naphthoic acid m-aminoanilide dissolved in 3 cc. alcohol, 1.2 cc. caustic soda 34 B. and .10 cc. hot water. The pH was about 10. After 30 minutes at approximately 110 F. 2 cc. formic acid was added. After another 30 minutes, the pH was about 5 and the leather was rinsed and refloated. 1.5 g. 5-butylsulfamyl-o-anisidine, pasted with water and dissolved with 1.5 cc. HCl 20 B. was added. After soaking for a few minutes .5 g. sodium nitrite previously dissolved in cold water was added. After 10 minutes 2 g. sodium acetate anhydrous was added. After 30 minutes the skin was rinsed and washed for 15 minutes with 2 g. soda ash and 2 g. sodium N-oleoyl-N-rnethyl tauride at 110 F. After rinsing, the skin was acidified with 1 cc. formic acid. A bright orangy-red was obtained of unusually uniform coloration. It had outstanding fastness to washing and dry cleaning.

Example 17 A 1 sq. ft. sample of chrome tanned syntan stained goat skin was wet back and floated with water. To the bath at approximately 110 F. was added 4 cc. formaldehyde (40% solution). After 10 minutes there was added 2.1 g. 3-hydroxy-2-naphthoic 4-amino-o-anisidide dissolved with 3 cc. alcohol and 1.5 cc. caustic soda 34 B. and hot water. The pH was 9-9.5. After 15 minutes there was added 4 cc. monoethanolamine. After 15 minutes there was added 4 cc. formic acid. After 30 minutes the pH was about 6 and the skin was rinsed and refloated. To the dyebath was added 1.8 g. S-butylsulfamyl-o-anisidine pasted with 10 cc. warm water and 2 cc. HCl. After a few minutes there was added 0.6 g. sodium nitrite dissolved in cold water. After 10 minutes there was added 2 g. sodium acetate anhydrous. After 30 minutes the skin was rinsed and finished as in Example 16.

A red dyeing was obtained of very uniform coloration, good penetration and very good fastness to washing and dry cleaning.

Example 18' Example 17 was repeated but employing as coupler 3-hydroxy-2-naphthoic-p-aminoanilide. A bluish-red was obtained of very good fastness to washing and dry cleaning. The grain was dyed very level.

Example 19 A 1 sq. ft. sample of chrome tanned syntan stained sheepskin was treated with coupler as in Example 16. After removing from the bath (pH 5) and rinsing, it was refloated in cold water. To this was added 8 g. S-butylsulfarnyl-2-methoxy-benzenediazonium chloride zinc chloride double salt dissolved in cold water. After about 40 minutes the skin was rinsed and finished as in Example 16. Results were about the same.

Example 20 A 1 sq. ft. sample of chrome tanned syntan stained sheepskin was treated with coupler as in Example 16. After removing from the bath (ph 5) and rinsing and refloating in cold water there was added to the bath 2 cc. formic acid followed by an addition of 1 /2 g. S-chloro-o-anisidine diazotized and stabilized with sarcosine and dissolved in cold water. After about 40 minutes the skin was rinsed and finished as in Example 16. A red dyeing was obtained of high degree of levelness.

Example 21 This example is the same as Example 16, but substituting for the coupler used in that example, Naphthol AS-D (3-hydroxy-2-naphthoic acid o-toluidide). A red color of improved fastness properties is obtained.

Example 22 This example is the same as Example 10, but employing instead of the Rapidogen mixture given there, dianisidine tetrazo stabilized with methyl taurine plus 3-hydroxy-2-naphthoic acid o-aminoanisidide. A uniform deep navy blue is obtained of good fastness properties.

Example 23 A 1 sq. ft. sample of chrome tanned syntan stained glove leather is treated for a few minutes in water containing 5 cc. 40% formaldehyde at 110-120 F. To this bath is added 1 g. phenyl methyl pyrazolone dissolved with 2 cc. alcohol and /2 cc. caustic soda 24 B. After minutes, 2 /2 cc. monoethanolamine is added. The pH of the bath is about 11. After 10 minutes, 12 cc. formic acid (10% solution) is added. After another 10 minutes, an additional 12 cc. formic acid is added. After another 10 minutes, wherein the pH is now about 6, the leather is removed and rinsed. The leather is refioated. To the bath is added 1.5 g. S-chloro-o-anisidine hydrochloride dissolved in sufficient water for solution and 1 cc. HCl. After 5 minutes, 6 cc. of a 10% sodium nitrite solution is added. After 20 minutes, 4 g. sodium acetate anhydrous is added. After 20 minutes, the leather is rinsed and finished as usual. The dyeing is yellow, having excellent fastness properties.

methyl pyrazolone. The yellow dyeing is very uniform, with excellent fastness properties.

This invention has been disclosed with respect to certain preferred embodiments, and various modifications and variations thereof will become obvious to the person skilled in the art. It is to be understood that such modifications and variations are within the scope of the appended claims.

This application is a continuation-in-part of application Serial No. 534,629, filed on September 15, 1955, now abandoned.

I claim:

1. A process for the azoic dyeing of leather comprising treating leather with an azoic coupling component devoid of sulfonic and carboxylic acid solubilizing groups and selected from the group consisting of pyrazolones and aromatic hydroxy compounds capable of coupling from an aqueous solution having an initial pH of more than 7 and less than 11 and containing a formaldehyde yielding substance selected from the group consisting of formaldehyde, paraformaldehyde, hexamethylenetetramine, and formaldehyde bisulfite, and a water-soluble lower nonaromatic amine of no more than 6 carbon atoms, lowering the pH of said solution to a final pH of no more than 7 over a period of from about 15 miuntes to 1.5 hours, and then treating the leather with a diazotized aromatic primary amine compound devoid of sulfonic and carboxylic acid solubilizing groups to produce its reaction product with said coupling component in situ.

2. A process as defined in claim 1 wherein said diazotized aromatic primary amine compound is employed in the form of a stabilized salt thereof.

3. A process as defined in claim 1 wherein said formaldehyde yielding substance is formaldehyde.

4. A process as defined in claim 1 wherein said diazotized aromatic primary amine compound is employed in a stabilized form thereof.

5. A process as defined in claim 4 wherein said stabilized form is the diazoamino compound.

6. A process as defined in claim 1 wherein said formaldehyde yielding substance is formaldehyde, said lower non-aromatic amine is monoethanolamine, and said diazotized aromatic primary amine is employed in a stabilized form thereof.

7. A process as defined in claim 6 wherein said diazotized aromatic primary amine is employed in the form of a stabilized salt thereof.

8. A process as defined in claim 6 wherein said stabilized form is the diazoamino compound.

References Cited in the file of this patent UNITED STATES PATENTS 1,718,882 Schwenk June 25, 1929 2,553,375 Kirst May 15, 1951 FOREIGN PATENTS 447,611 Great Britain May 14, 1936 707,884 Great Britain Apr. 28, 1954 OTHER REFERENCES Venkataraman: Synthetic Dyes, 1952, vol. I, pp. 699 and 670, Academic Press, N.Y. 

1. A PROCESS FOR THE AZOIC DYEING OF LEATHER COMPRISING TREATING LEATHER WITH AN AZOIC COUPLING COMPONENT DEVOID OF SULFONIC AND CARBOXYLIC ACID SOLUBILIZING GROUPS AND SELECTED FROM THE GROUP CONSISTING OF PYRAZOLONES AND AROMATIC HYDROXY COMPOUNDS CAPABLE OF COUPLING FROM AN AQUEOUS SOLUTION HAVING AN INITIAL PH OF MORE THAN 7 AND LESS THAN 11 AND CONTAINING A FORMALDEHYDE YIELDING SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, PARAFORMALDEHYDE, HEXAMETHYLENETETRAMINE, AND FORMALDEHYDE BISULFITE, AND A WATER-SOLUBLE LOWER NONAROMATIC AMINE OF NO MORE THAN 6 CARBON ATOMS, LOWERING THE PH OF SAID SOLUTION TO A FINAL PH OF NO MORE THAN 7 OVER A PERIOD OF FROM ABOUT 15 MINUTES TO 1.5 HOURS, AND THEN TREATING THE LEATHER WITH A DIAZOTIZED AROMATIC PRIMARY AMINE COMPOUND DEVOID OF SULFONIC AND CARBOXYLIC ACID SOLUBILIZING GROUPS TO PRODUCE ITS REACTION PRODUCT WITH SAID COUPLING COMPONENT IN SITU. 